1. Field of the Invention
The present invention relates to a differential transmission cable and a multipair differential transmission cable.
2. Description of the Related Art
There is a known a differential transmission cable having the following structure: a pair of insulated wires, each including an inner conductor and an insulator covering the inner conductor, are arranged parallel to each other; an outer conductor (shield) is formed by winding a metal tape around the pair of insulated wires; and a wrapping tape is wound around the outer conductor so that the metal tape may not become loose.
Such a differential transmission cable has a problem in that, when the outer conductor is directly soldered to a ground pattern of a printed circuit board or the like, the insulator may become damaged (deformed) due to heat during soldering and therefore the connection yield is decreased.
To address the problem, a differential transmission cable including a drain wire for grounding the outer conductor is used. The drain wire is electrically connected the outer conductor, and the outer conductor can be grounded through the drain wire by electrically connecting the drain wire to a ground pattern of a printed circuit board or the like.
Typically, a drain wire is disposed inside of the outer conductor. However, the drain wire may be disposed outside of the outer conductor, that is, between the outer conductor and the wrapping tape.
Japanese Unexamined Patent Application Publication Nos. 2001-93357 and 2011-86458 describe technologies related to the present application.
However, when the drain wire is disposed inside of the outer conductor, a problem arises in that properties of the cable, such as intra-pair skew and Scd21, may become degraded if the position of the drain wire is displaced only slightly.
When the drain wire is disposed between the outer conductor and the wrapping tape, a problem arises in that the metal tape is not sufficiently pressed by the wrapping tape and therefore properties of the cable, such as intra-pair skew and Scd21, may become degraded.